Self-activated cathode substrates in rechargeable zinc–air batteries

Abstract Developing cost-effective and durable air-cathodes is crucial for improving metal-air batteries. Most reports of cathode formulation involve preparing bi-functional electrocatalysts from wet chemistry or solid-state synthesis, followed by pasting onto a substrate. In this work, the cathodes generated from electrochemical activation of normal carbon paper substrates were directly used in Zn-air batteries. The self-activated carbon paper substrate without any additional electrocatalysts exhibits an impressive cycling stability (more than 165 hours for 1,000 cycles) and a small discharge-charge voltage gap. After the activation, the maximum power density and electrochemical surface area were increased by over 40 and 1,920 times respectively. It is discovered that substrates after activation can be directly used as a cathode. The new method is scalable, inexpensive and produces near best in class performance. The mechanism behind this enhancement is due to the creation of oxygen functional groups within the cathode, which overcame slow kinetics, enhanced wettability and enabled optimum three-phase boundaries.